Nudibranch species found during tide pooling

KNOW YOUR NUDIBRANCHS:NUDIBRANCHS FROM NEW ENGLAND

This post is a fun post about the four nudibranch species I found in the intertidal rocks of Nahant, MA while tidepooling in the Spring 2025.

NUDIBRANCHS (nudus: Naked; brankhia: gills)

Nudibranchs are marine soft-bodied mollusks which have two main characteristics. They lack a shell unlike any other snail/mollusk and have external gills either in the form of gill plume or cerata.

There are typically two kinds of nudibranchs:

A. Dorid Nudibranch- Flat disc shaped body, external gills on the back looking like a plume or tree.Sometimes when they feel threatened, they retract their gills inside the body.

Image: A Dorid Nudibranch( Goniobranchus trimarginatus ) in the intertidal of India.

B. Aeolid Nudibranch- Unlike dorids, aeolids have a narrow mantle with finger like extensions/projections called as the cerata (external gills in aeolids). The tips of the ceratas stored cnidosacs containing nematocysts obtained from their food sources like sea anemones, hydroids or other cnidarians.

Image: A aeolid Nudibranch( Coryphella trilineata ) on the Friday Harbor Laboratory Docks.

1. Dendronotus frondosus-Bushy-backed nudibranch

• Image 1: Nudibranch in the intertidal

Image 2: Headshot of the nudibranch

2. Ancula gibbosa-Humped Ancula Sea Slug

Nudibranch in the intertidal

Feeding on hydroids

3. Archidoris pseudoargus-Sea Lemon

• Belongs to the dorid type nudibranchs.
• Dorid Nudibranchs have external gills (can see in Image 2) on their back that looks like a plume or tree.

Nudibranch in the intertidal

Gills of the dorids

4. Aeolidia papillosa-Shag-rug nudibranch

Nudibranch on the mussel bed